Mutant bacterial strains of the genus Sphingomonas deficient in production of polyhydroxybutyrate and a process of clarification of sphingans and compositions thereof

Abstract

The invention relates to mutant strains of the genus Sphingomonas which have a mutation in at least one gene encoding a protein involved in polyhydroxybutyrate (“PHB”) synthesis that allows the mutant strains to produce PHB-deficient Sphingans. The invention is also directed to a process for preparing a clarified Sphingan solution comprising heating aqueous Sphingan solution, in particular PUB-deficient Sphingan solution, to a clarification temperature of about 30° C. to about 70° C., and treating the solution with a clarification agent and enzymes. In addition, the invention is directed to a food or industrial product comprising a PHB-deficient and/or clarified Sphingan. One particular embodiment of the invention is directed to a clarified, PHB-deficient high-acyl gellan and the processes of making thereof.

The invention claimed is: 
     
       1. An isolated DNA from a mutant strain of a genus  Sphingomonas , wherein said DNA comprises a mutated phaC gene encoding a polyhydroxybutyrate (PHB) synthase, and wherein said mutant strain produces sphingan without producing PHB. 
     
     
       2. The isolated DNA of  claim 1 , wherein said DNA comprises a nucleotide sequence set forth in SEQ ID NO:7. 
     
     
       3. The isolated DNA of  claim 2 , wherein said DNA further comprises flanking regions. 
     
     
       4. The isolated DNA of  claim 3 , wherein said DNA comprises a nucleotide sequence set forth in SEQ ID NO:13. 
     
     
       5. The isolated DNA of  claim 1 , wherein said PHB synthase comprises an amino acid sequence set forth in SEQ ID NO:8. 
     
     
       6. A vector comprising the isolated DNA of  claim 1 . 
     
     
       7. A vector comprising the isolated DNA of  claim 2 . 
     
     
       8. A vector comprising the isolated DNA of  claim 3 . 
     
     
       9. A vector comprising the isolated DNA of  claim 4 . 
     
     
       10. The isolated DNA of  claim 1 , wherein said sphingan is gellan, diutan (S-657), welan (S-130), rhamsan (S-194), S-198, S-7, S-88, NW-11, or B-16. 
     
     
       11. The isolated DNA of  claim 1 , wherein said sphingan is gellan. 
     
     
       12. The isolated DNA of  claim 1 , wherein said sphingan is diutan. 
     
     
       13. A recombinant DNA comprising a mutated phaC gene encoding a polyhydroxybutyrate (PHB) synthase, wherein a  Sphingomonas  strain comprising said recombinant DNA produces sphingan without producing PHB. 
     
     
       14. The recombinant DNA of  claim 13 , wherein said DNA comprises a nucleotide sequence set forth in SEQ ID NO:7. 
     
     
       15. The recombinant DNA of  claim 14 , wherein said DNA further comprises flanking regions. 
     
     
       16. The recombinant DNA of  claim 15 , wherein said DNA comprises a nucleotide sequence set forth in SEQ ID NO:13. 
     
     
       17. The recombinant DNA of  claim 13 , wherein said PHB synthase comprises an amino acid sequence set forth in SEQ ID NO:8. 
     
     
       18. A recombinant vector comprising the recombinant DNA of  claim 13 . 
     
     
       19. A recombinant vector comprising the recombinant DNA of  claim 14 . 
     
     
       20. A recombinant vector comprising the recombinant DNA of  claim 15 . 
     
     
       21. A recombinant vector comprising the recombinant DNA of  claim 16 . 
     
     
       22. The recombinant DNA of  claim 13 , wherein said sphingan is gellan, diutan (S-657), welan (S-130), rhamsan (S-194), S-198, S-7, S-88, NW-11, or B-16.